Photographic printing apparatus

ABSTRACT

A photographic printing apparatus, particularly for exposing lithographic plates to light through films, in which a plate with a film thereon is applied to a conveyor at an input station and conveyed by the conveyor to a position within a vacuum frame unit at an exposure station, after which the vacuum frame is closed and evacuated for pressurizing the plate and film, the exposure is made, the vacuum frame unit is opened, and operation of the conveyor is resumed to convey the plate and film out of the vacuum frame unit to an output station for removal of the film.

Harrell et al.

Jan. 18, 1972 [54] PHOTOGRAPHIC PRINTING Primary Examiner-Samuel S.Matthews APPARATUS Assistant Examiner-Richard L. Moses Attorney-Koemg,Senmger, Powers and Leavitt [72] Inventors: Robert E. Harrell,Manchester; Edward B.

Parker, Ballwin, both of Mo. [57] ABSTRACT [73] Assignee: Western LithoPlate & Supply Co., St. A photographic printing apparatus, particularlyfor exposing Louis, Mo. lithographic plates to light through films, inwhich a plate with [22] Filed: Oct. 31, 1969 a film thereon 1s applledto a conveyor at an input statlon and conveyed by the conveyor to aposition within a vacuum frame [21] App]. No.: 872,867 unit at anexposure station, after which the vacuum frame is closed and evacuatedfor pressurizing the plate and film, the exposure is made, the vacuumframe unit is opened, and [52] US. cl ..355/85, 355/91, 355/99 operationof the conveyor is resumed to convey the plate and l (1|. ..C03b out ofthe acuum frame n t to an output Station for [58] Held olSearch..355/85,87,9l,93,99,101; removalofthe mm 27 Claims, 9 Drawing Figures[56] References Cited UNITED STATES PATENTS 3,468,606 9/1969 Wolf et al...355/91 /35' /55 a /2 h V V2 7 5 /45 0 75 n l w 4 93 1/ 59 7 73 1/ h u29,; I 33 35 3a i 5/ Z 3 7 A 47 4/ i (/5 45 47 PATENTEU JAN? 81972 SHEET2 0F 7 PATENTED JAN: 81972 SHEET 3 UF 7 BACKGROUND OF THE INVENTION Thisinvention relates to photographic printing apparatus, and moreparticularly to apparatus for automatically carrying photosensitiveplates through an exposure operation.

The invention is particularly concerned with apparatus for automaticallycarrying lithographic plates such as are widely used in offset printingthrough an exposure operation. It will be understood that a typicallithographic plate generally comprises a thin aluminum plate having aphotosensitive coating on one face thereof, e.g., a coating of a diazocompound, to be exposed to light through a film (e.g., a negative) fordevelopment of an image on the plate. Heretofore, the exposure of suchplates has been typically carried out by relatively slow and cumbersomemanual procedure involving manually placing a plate and film in a vacuumprinting frame, manually closing the frame, exposing the plate to lightthrough the film, manually opening the frame, and manually removing theplate and film from the frame. The present day demands, particularly innewspaper operations, for rapid processing of lithographic plates foroffset printing are not readily economically met by such manualprocedure.

SUMMARY OF THE INVENTION Among the several objects of this invention maybe noted the provision of a photographic printing apparatus,particularly for exposing lithographic plates, adapted automatically toeffect the handling of plates and films through the exposure procedure,including pressurizing of the plates and films for close contacttherebetween during the exposure; the provision of such apparatus whichmay be used in tandem with automated plate processing equipment fordeveloping the images on the plates; and the provision of such apparatuswhich minimizes the number of quality of manual operations required forreliable exposure of the plates. In general, apparatus of this inventioncomprises an endless conveyor which is movable intermittently to conveya plate with a film thereon from an input station, at which a plate andfilm are applied to the conveyor, to an exposure station, at which theplate is exposed to light through the film, and thence to an outputstation. A light-transmitting pressing means is provided for pressingthe plate and film at the exposure station, and means is provided formounting this pressing means for movement from an open retractedposition spaced from the conveyor, to permit the conveyor to convey aplate and film from the input station to the exposure station, to aclosed position for pressing the assembly at the exposure station, saidpressing means being movable to its said open retracted position afterexposure of a plate to permit the conveyor to move the exposed plate andfilm out of the exposure station to the output station. A light sourceis provided at the exposure station for exposing the plate at theexposure station through the film on the plate while pressed by saidlight-transmitting pressing means. Other objects and features will be inpart apparent and in part pointed out hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS line 6-6 of FIG. 2, with parts brokenaway;

FIG. 7 is an enlarged vertical transverse section taken on line 7-7 ofFIG. 2, with parts broken away;

FIG. 8 is a wiring diagram; and

FIG. 9 is a chart showing the timing of certain cam-actuated switches.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first moreparticularly to FIGS. 1 to 3 of the drawings, a photographic printingapparatus made in accordance with this invention is shown to comprise anendless conveyor generally designated 1 movable intermittently to conveya light-sensitive plate P with a film F thereon from an input station I,at which the plate and the film are applied to the conveyor, to anexposure station E, at which the plate is exposed to light through thefilm, and thence to an output station 0 for removal of the film from theplate. The apparatus is particularly useful for exposing lithographicplates having a light sensitive coating on one surface thereof, but maybe used for exposing photographic plates other than lithographic plates.Generally indicated at 3 is a light-transmitting means for pressing theplate film assembly at the exposure station. Means generally designated5 is provided for mounting this light-transmitting means for movementfrom an open retracted position spaced from the conveyor to permit theconveyor to convey a plate film assembly (the work) from the inputstation I to the exposure station E to closed position for pressing theassembly (the work) at the exposure station. A light source 7 isprovided at the exposure station for exposing the work at the exposurestation while the work is pressed by the light-transmitting means 3. Thearrangement is such that a plate with a film thereon may be applied tothe conveyor at the input station I, the conveyor then driven to conveythis item of work to the exposure station E under the pressing means 3(which is open at this time), after which the pressing means is closed,the light source activated to expose the plate to light through thefilm. Then, the light source is deactivated, the pressing means isopened, and the conveyor is driven to convey the exposed work out of theexposure station to the output station for removal.

The conveyor 1 comprises an elongate table designated in its entirety bythe reference numeral 9 having a top 11 supported on legs 13 located atthe sides of the table adjacent its four corners. The table top 11comprises a channel 15 extending lengthwise of the table along one sidethereof (its left side as viewed in the direction of travel of theplate-film assemblies), and a channel 17 extending lengthwise of thetable along its other side. These channels are positioned with theirwebs horizontal and their flanges extending downward, the legs 13 beingwelded to the outside of the outside flanges of the channels. Braces 19extend between the legs at the sides of the table, and braces 21 extendbetween the legs at its ends. A sheet metal table top plate 23horizontally spans the channels at the input station I and a sheet metaltable top plate 25 horizontally spans the channels at the output station0. These table top plates are generally coplanar and their inner ends23a and 25a are spaced apart to provide a gap therebetween at theexposure station. The side edges of the plates 23 and 25 are spacedinward from the outer sides of the channels.

The conveyor 1 further comprises a pair of endless chains eachdesignated 29 having horizontal upper reaches 29a. These chains arearranged for travel of said horizontal upper reachs 29a lengthwise ofthe table above the channels 15 and 17 outward of the side edges of theplates 23 and 25. The chains are trained around sprockets 31 on ahorizontal drive shaft 33 at the output station end of the table (whichmay he referred to as its forward end) and around s rockets 35 on ahorizontal idler shaft 37 at the input station and (the rearward end) ofthe table. Shaft 33 extends transversely of the table, being joumaled inbearings 39 carried by brackets as indicated at 41 on the channels 15and 17 at their forward ends. it is adapted to be intermittently drivenfor forward feed of the upper reaches of the chains via a chain drive 43from an electric gearmotor 45. Shaft 37 extends transversely of thetable, being joumaled in bearings 47 carried by brackets as indicated at49 on the channels at their rearward ends. The upper reaches 29a ofchains 29 are guided for travel along the channels and 17 by tracks 51on the channels. Extending between the chains at equally spacedintervals along their length are flat bars 53, the ends of these barsbeing secured to the chains with the bars in position for travelflatwise over the table top plates 23 and 25 contiguous to the latter.Each bar has means thereon for attachment thereto of a plate P and afilm F with the plate and film in proper register. As shown in FIGS. 2and 5, this means comprises a pair of pins 55 on the bar, the plate Pand film F each having a pair of holes such as indicated at 57 adjacentone edge thereof for receiving the pins, the holes being located forproper registry of the film with the plate when the plate and the filmare applied to the pins.

The pressing means 3 is constituted by a vacuum frame unit comprising awindow assembly 59 having a light-transmitting panel 61, and a flexibleresilient presser pad 63 below the window assembly, adapted for vacuumpressing of a plate and a film therebetween (see especially FIGS. 6 and7). The pad 63, which may comprise a relatively thick slab of arelatively closed-cell foam rubber, for example, is mounted on a sheetmetal bottom plate 65 spanning the channels 15 and 17 in the gap betweentheir inner ends 23a and 25a at the exposure station. The side edges ofthe plate 65 and pad 63 are spaced inward from the outer sides of thechannels, like the plates 23 and 25. The pad is cemented airtight to thebottom plate 65 all around its margin as indicated at 67, the portion ofthe pad bounded by the cement being free of the bottom plate so that isis adapted to flex upward from the bottom plate under a vacuum conditionas will appear. Normally, the top surface of the pad is generally flushwith the top surfaces of the table top plates 23 and 25.

The window assembly 59 is mounted in an open rectangular frame generallydesignated 69 for up and down movement relative to the frame. The frame69 is normally located in horizontal position overlying the table topand spaced above the table top at the exposure station, the spacingbeing sufficient to allow for passage of a plate P with a film F thereonalong the table top underneath the frame. The frame comprises side anglebars 71 and 73 (71 being at the left and 73 at the right) which extendlongitudinally with respect to the table and two flat end bars eachdesignated 75 which extend transversely with respect to the table. Bars75 are disposed vertically. The frame 69 is pivoted for swingingmovement on a horizontal axis extending longitudinally of the table atthe left side of the table by means of hinges such as indicated at 77each having one leaf secured to the outside of channel 15 and the othersecured to bar 71. It normally rests in horizontal position as shown inFIG. 7 extending across the table, its right side angle bar 73 bearingon stops 79 extending up from the right side channel 17, and is adaptedto be swung up from this position when desired to open it away from thetable top, springs 81 being provided to counterbalance its weight plusthat of the window assembly 59 and other components carried thereby.

The window assembly 59 comprises an open rectangular window frame 83,the light-transmitting panel 61 being secured at the bottom of thisframe 83 by clips 85 with a gasket 87 interposed therebetween to providean airtight seal between the frame 83 and the panel 61. The latter mayconsist of a relatively rigid panel of any suitable light-transmittingplastic, or a pane of glass. The window assembly 59 is mounted forvertical movement in the frame 69, and means indicated generally at 89is provided for moving it vertically relative to the frame 69 between araised retracted position relative to the presser pad 63 and a closedposition wherein a peripheral sealing strip 91 adhered to the bottom ofpanel 61 is in sealing engagement with the pad. When the window assembly59 is in its raised retracted position, the sealing strip 91 is spacedabove the upper surface of pad 63 for passage of a bar 53 and workmoving with the bar.

The means 89 for vertically moving the window assembly 59 in the frame69 includes a pair of cam plates each designated 93 guided for slidingmovement transversely of the frame 69 on the inside of bars 75 of theframe by means of guides 95 secured to bars 75. The cam plates areinterconnected for conjoint movement by an angle bar 97 which extendsbetween the ends of the cam plates adjacent the side angle bar 71 offrame 69. An air cylinder 99 is secured to bar 71 extending laterallyoutward therefrom. A piston rod 101 extends from a piston (not shown) incylinder 99 to a connection at 103 with bar 97. Operation of cylinder 99is controlled by a solenoid valve V. The arrangement is such that onextension of the piston rod from cylinder 99, the cam plates 93 aremoved in the direction away from bar 71 toward bar 73 and when thepiston rod is retracted into the cylinder, the cam plates are retractedback toward bar 71. Each cam plate has a pair of inclined cam slots 105.Extending up from each of the two transversely extending sides of thewindow frame 83 of window assembly 59 are two lugs each designated 107.Shafts 109 at the upper end of these lugs carry cam follower rollers 111slidable in these inclined slots. These shafts also carry rollers 113slidable in vertical slots 115 in the bars 75 guiding the window frame83 for vertical movement relative to the bars 75. The cam slots 105 areso angled that when cam plates 93 are moved in the direction away frombar 71 (toward the right as viewed in FIG. 7), the window assembly 59 ismoved down to its closed position wherein sealing strip 91 engages thepresser pad 63, and when cam plates 93 are moved back toward bar 71, thewindow assembly is raised to its retracted position.

The presser pad 63 has an opening 117 therethrough (inward of itscemented margin 67) constituting a vacuum port, and is provided with afitting 119 on its bottom for this port with a vacuum line 121 connectedbetween this fitting and the inlet of a vacuum pump 123 driven by anelectric motor 125 (see FIG. 1).

Extending up from bars 75 are posts 127 carrying bars 129 supporting thelight source 7, which may be a high-intensity light source such as anAscor ADDALUX light source made by Berkey Technical Corporation ofWoodside, New York. Bars 129 are vertically adjustable on the posts asindicated at 131 and the light source is adjustable on the bars 129 asindicated at 133. The light source is ofa type which has an exposurelamp which is continuously energized during the working period and ashutter, exposure intervals being determined by the opening and closingof the shutter. It has a blower 135 on top thereof.

A microswitch 137 is mounted underneath the table plate 23 at the inputstation I and has its operating arm 139 projecting upward through anopening 141 in plate 23 for engagement by a lithographic plate P placedon plate 23 (see FIGS. 2 and 5). A microswitch 143 is mounted at theoutput or exit end of the table 9 in position for raising of itsoperating arm 145 by a bar 53 as it reaches the exit end of the tabletop plate 25 at the unloading station U. I

Now, referring to FIG. 8, the control circuit for the apparatus is shownto include five latching relays denoted lLR-SLR, two timing relaysdenoted lTR and 2TR, a variable timing relay denoted VTR, and twocontrol relays denoted 1CR and 2CR. Each of the five latching relays hasa lower coil denoted by the letter D, an upper coil denoted by theletter U (e.g., the lower coil of lLR is lLRD and the upper coil of lLRis ILRU). Each of the five latching relays is of a type having contactsassociated with its upper coil, designated lLRD-l, for example, andcontacts associated with its upper coil, designated lLRV-l, for example,and as to which all its contacts are latched in one position onenergization of the lower coil and remain latched in that position ondeenergization of the lower coil, becoming latched in their otherposition on energization of the upper coil and remaining latched thereinon deenergization of the upper coil.

A pushbutton switch lPB is connected in series with the lower coil lLRDof relay lLR and contacts 4LRD-l (shown closed) of relay 4LR in a line151 across line L1 and neutral line N of a three phase 230 volt powersupply circuit, the third line of this circuit being indicated at L2. Amain switch 18 is provided in lines L1 and L2. A lamp PO is connected ina line 153 across lines L2 and N to indicate that power is on whenswitch 1S is closed. A switch 155 is connected in series with the coilof relay 2CR in a line 157 across L1 and N. This switch 155, when open,provides for automatic cycling of the apparatus and when closed toenergize relay 2CR provides for manual operation. Contacts 4LRD-2 (shownclosed) of relay 4LR are connected in series with a lamp R in a line 159across L1 and N. The solenoid valve V is connected in series withcontacts lCR-l (shown closed) of relay 1CR and a normally opencam-actuated switch 1CS-3 in a line 161 across L1 and N. The switch1CS-3 is one of seven cam-actuated switches lCS-l, 1CS-2, lCS-3, 1CS-4,1CS-5, lCS-8, and 1CS-9 actuated by timing cams on a timer shaft (notshown) driven by a timer motor 1CS.

Contacts SLRD-l (shown open) of relay SLR are connected in series withcoil VTRC of relay VTR in a line 163 across L1 and N. Relay VTR has amotor VTRM and normally closed contacts VTR-l connected in series in aline 164 shunted around its coil VTRC. Relay VTR is adapted, via itsmotor VTRM, to time out the exposure interval. Normally open contactsVTR-2 of relay VTR and the upper coil SLRU of relay SLR are connected inseries in a line 165 across L1 and N. Contacts 5LRD-2 (shown closed) ofrelay SLR, contacts 2LRD-1 (shown open) of relay 2LR and the motor 1CSfor driving the timer shaft carrying the timing .cams which actuate theseven lCS switches are connected in series in a line 167 across L1 andN. Switch 143 and the brake coil 1MB of the conveyor drive motor 45 areconnected in series in a line 169 across L1 and N. Coil 1MB whendeenergized applies a brake to the motor shaft, and releases the brakewhen energized. Cam switch lCS-l (which is normally open) is con nectedin series with motor 45 in a line 171 across L1 and N. Lines 169 and 171are interconnected as indicated at 173 so that the coil 1MB and motor 45are in parallel.

Contacts 4LRU-l (shown open) of relay 4LR are connected in series withan off cycle" lamp CC (to indicate that a cycle is off) in a line 175across L1 and N. Contacts 4LRU-2 (shown open) of relay 4LR are connectedin series with the coil of timing relay 2TR in a line 177 across L1 andN. Normally closed contacts 2CR-1 of relay 2CR, contacts 3LRD-1 (shownopen) of relay 3LR and the coil 4LRU of relay 4LR are connected inseries in a line 179 across L1 and N. Cam-actuated switch 1CS-9 (whichis normally closed), contacts 3LRD-3 (normally open) of relay 3LR,contacts 2LRU-1 of relay 2LR and the upper coil 2LRU of relay 2LR areconnected in series in a line 181 across L1 and N. The upper coil SLRUof relay 3LR is connected in a line 183 in shunt with the upper coil2LRU of relay 2LR. Cam-actuated switch 1CS-8 (which is normally open)contacts 3LRU-1 (normally closed) of relay 3LR and a counter 185 areconnected in series in a line 187 across L1 and N. Normally opencontacts lTR-l of relay lTR, normally open contacts 1370 of switch 137and the lower coil 2LRD of relay 2LR are connected in series in a line189 across L1 and N. Normally closed contacts 137s of switch 137,cam-actuated switch 1CS-2 (which is normally open) and the lower coil3LRD of relay 3LR are connected in series in a line 191 in parallel withcontacts 1370 and the lower coil 2LRD of relay 2LR.

The upper coil lLRU of relay lLR is connected in a line 193 in parallelwith the lower coil 3LRD of relay SLR. Normally closed contacts lTR-Z ofrelay lTR, normally open contacts 2CR-2 of relay 2CR and a lamp 0 toindicate ON are connected in a line 195 in parallel with contacts 137C,contacts lCS-2 and the lower coil 3LRD of relay 3LR.

Contacts lLRD-l (shown open) of relay lLR, normally closed contacts2CR-3 of relay 2CR, contacts 1LRD-2 (shown open) of relay lLR and thecoil of relay lTR are connected in series in a line 197 across L1 and N.Lines 195 and 197 are interconnected as indicated at 199. Normally opencontacts ZTR-l of relay 2TR and the lower coil 4LRD of relay 4LR areconnected in series in a line 201 across L1 and N. Contacts 3LRU-1(shown open) of relay 3LR and the coil of relay lCR are connected inseries in a line 203 across L1 and N. Cam-actuated switch lCS-S,normally closed contacts lCR-2 of relay lCR and the lower coil SLRD ofrelay 5LR are connected in series in a line 205 across L1 and N.

The motor for driving the vacuum pump is connected in series withnormally closed contacts lCR-3 or relay lCR and with cam-actuated switch1CS-4 (which is normally open) in a line 207 across lines L2 and N. Thelamp 209 of the light source 7 has a control 211 in a circuit 213including contacts lLRU-l (shown closed) of relay lLR, normally closedcontacts 2CR-4 of relay 2CR, contacts 1LRU-2 (shown open) of relay lLRand normally open contacts 2CR-5 of relay 2CR. The lamp 209, once turnedon, remains on and the light source 7 has a shutter (not shown) which iselectrically opened to expose a plate at station E for a predeterminedinterval under control of the variable timing relay VTR. Lines L1, L2and N are connected to the input 215 of the light source 7 as indicatedat 217. Normally open contacts VTRl of relay VTR are connected in acircuit 219 for a shutter actuator 221.

Operation is as follows:

For automatic cycling of the apparatus (i.e., for automatically feedingone plate after another through the apparatus) main switch 15 is closedand switch is open. With 18 closed, lamp PO is energized to indicate thepower is on. Latch relays 1LR, 2LR, 3LR and SLR will have previously hadtheir upper coils U energized and their contacts accordingly are set asshown in FlG. 8. Latch relay 4LR will have previously had its lower coilD energized and its contacts accordingly are set as shown in FIG. 8. Thewindow assembly 59 is in its raised retracted position. Lamp R isenergized to indicate that the apparatus is ready to start cycling. Afirst lithographic plate P with a film F thereon is placed on the tabletop plate 23 at the input station I, and attached to the bar 53 which isabout to enter the exposure station E. The plate P holds down theoperating arm 139 of switch 137 (see FIG. 5) so that contacts 1370 ofthis switch are open and contacts 1370 are closed.

The pushbutton switch lPB is momentarily closed, resulting inenergization of the lower coil lLRD of latch relay lLR.

This closes contacts lLRD-l and lLRD-2 in line 197, and opens contactslLRU-l and closes contacts lLRU-Z in circuit 213. The efl'ect of openinglLRU-1 and closing lLRU-2 is to energize the exposure lamp 209. Closureof lLRD-l and 1LRD-2 in line 197 energizes the coil of timing relay lTR(contacts 2CR-3 being closed), and energizes lamp 0 to in dicate thatthe apparatus has been turned on.

After its built-in time delay interval(e.g., 1 minute), relay lTR closesits contacts lTR-l in line 189 and opens its contacts 1TR-2 in line 195.On closure of contacts lTR-l in line 189 and assuming that contacts 1370of switch 137 are closed via a lithographic plate P on table plate 23 atthe input station l holding down arm 139 of switch 137, the lower coil2LRD of latch relay 2LR is energized, closing contacts 2LRD1 in line 167and contacts 2LRU-1 in line 181. On closure of contacts 2LRD-1 in line167, timing motor ICS is energized to drive the timer shaft whichcarries the cams for actuating the seven lCS switches.

The operation of the cam switches is shown in FIG. 9. Referring thereto,it will be seen that lCS-l is closed at 2 seconds of running time ofmotor lCS from the start of motor lCS, and opened at 5 seconds. Switch1CS-2 is closed at 2% seconds and opened at 4 seconds of running time ofmotor 1CS. Switch 1CS-3 is closed at 8 seconds and opened at 22% secondsof running time of motor 1CS. Switch 1CS-4 is closed at 8 seconds andopened at 22 seconds. Switch 1CS-5 is momentarily closed at 20 seconds.Switch 1CS-8 is closed at 22% seconds and opened at 22% seconds. Switch1CS-9 is closed at 23 seconds and opened at one-fourth s second ofrunning time.

On closure of switch 1CS-l (in line 171), motor 45 is energized to drivethe conveyor chains 29 and move bars 53 forward, thereby pulling thelithographic plate P with film F thereon forward from the input stationl into the exposure station E. As soon as the bar 53 which was underoperating arm 145 of switch'143 at the exit end of the table top plate25 moves out from under this arm, switch 143 (in line 169) closes toestablish a holding circuit for motor 45 via line 173. Switch lCS-lopens at seconds, but motor 45 remains energized via said holdingcircuit until it is broken by the opening of switch 143 when the nextbar 53 comes under the switch operating arm 145. This occurs at about 7seconds of elapsed time, and at this point the first lithographic plateP with the film F thereon has been advanced from the input station Icompletely into the exposure station E under the window assembly 59,ready for lowering of the latter for pressurizing the plate P and filmF.

At 2% seconds of elapsed running time of motor lCS, switch lCS-2 closesand remains closed until the 4th second, but has no effect at this timesince contacts 137s of switch 137 in line 191 with switch lCS-2 are opendue to the first lithographic plate P continuing to hold down arm 139 ofswitch 137.

At 8 seconds of elapsed running time of motor lCS, switches lCS-3 (inline 161) and lCS-4 (in line 207) close. With lCS-3 closed in line 161,and contacts lCR-l closed, solenoid valve V is energized to actuate aircylinder 99 to extend piston rod 101 and lower the window assembly 59 toits closed position wherein sealing strip 91 engages the presser pad 63all around the first plate P and film P which have been pulled into theexposure station E. With switch 1CS-4 closed in line 207 and contacts1CR-3 closed, motor 125 is energized to drive the vacuum pump 123 todraw a vacuum in the sealed chamber defined by the light-transmittingpanel 61, strip 91 and presser pad 63, in which is received the firstlithographic plate P with the film F on top. As a consequence of drawingthe vacuum in this chamber, pad 63 is pressed upward by atmospheric airpressure on its bottom, thereby to press the stated first plate P andfilm F against the light-transmitting panel 61, so that the plate ismade ready for exposure. Plate 65 has a central hole 65a for entry ofair to pass against the bottom of the pad.

At seconds, cam switch lCS-S (in line 205) closes momentarily, and withcontacts lCR-Z in line 205 closed, the lower coil SLRD of latch relaySLR is energized to close contacts SLRD-l (line 163) and to opencontacts SLRD-2 (line 167). With contacts SLRD-l closed, the coil VTRCand motor VTRM of the variable timing relay VTR are energized. Onopening of contacts 5LRD-2 in line 167, the timing motor ICS isdeenergized. On energization of coil VTRC, contacts VTR-l of relay VTRclose in circuit 219 to effect actuation of shutter actuator 221 to openthe shutter of the light source 7, thereby exposing the lithographicplate P at the exposure station to light from lamp 209 through thelight-transmitting panel 61 and the film F under pressed flat conditionsof the plate and film.

The motor VTRM of the variable timing relay VTR times out the exposureinterval, at the termination of which contacts VTR-J in line 164 open tostop motor VTRM and contacts VTR-2 in line 165 close to energize theupper coil SLRU of relay SLR. This opens contacts SLRD-l in line 163 andcloses contacts 5LRD2 in line. 167. Opening of contacts SLRD-ldeenergizes relay coil VTRC. Closing of contacts SLRD-Z in line 167restarts the timing motor 1C8 (contacts ZLRD-l being closed at thistime). Opening of contacts VTR! in circuit 219 causes the shutter toclose and terminate the exposure.

At 22 seconds of elapsed running time of motor lCS, switch lCS-4 opensthereby deenergizing the motor 125 to stop the vacuum pump 123.

At 22% seconds, switch lCS-3 opens to deenergize the solenoid valve Vand actuate the air cylinder 99 to retract piston rod 101 and raise thewindow assembly 59 to its retracted position clear of the plate and filmat station E. This enables exit of the exposed plate P and the film Fthereon from the exposure station E. Switch lCS-8 is closed from 22% to22% seconds to energize the counter 185 (contacts 3CRU-1 being closed atthis time).

The timing motor lCS continues to run through 0 and at 2 seconds ofrunning time from 0, switch lCS-l closes, starting the motor 45 toresume operation of the conveyor 1. Shortly after the motor 45 starts,and the bar 53 which was under the operating arm 145 of switch 143 movesout from under this arm, switch 143 (in line 169) closes to establishthe holding circuit for motor 45 via line 173. Switch lCS-l opens at 5seconds, but motor 45 remains energized via said holding circuit untilit is broken by the opening of switch 143 when the next bar 53 comesunder the arm 145. This occurs at about 7 seconds, and at this point theexposed lithographic plate P with the film F thereon has been pulledforward out of the exposure station and onto the table top plate 25 atthe output station 0. The exposed plate and the film may then be removedfrom table top plate 25. it is contemplated that the film may be removedfrom the exposed plate as by means of a vacuum cup lifter, and theexposed plate fed directly ahead to a plate processing apparatus.

Assuming that a second plate P to be exposed and a film F were appliedto table top plate 23 at the input station land attached to the bar 53inposition to enter the exposure station E during the dwell of the bars 53after entry of the first plate P and film thereon into the exposurestation, the second plate P with a film F thereon is pulled into theexposure station when the first plate and film are pulled out of theexposure station to the output station and the above-describedoperations are repeated for exposing the second plate P and then pullingit forward out of the exposure station to the output station.

The apparatus continues to cycle automatically as above described aslong as plates P are applied one after another to the table top plate 23at the input station during successive dwells of the conveyor 1. Thelast plate P with a film-F to be applied is carried through an exposureoperation and pulled out to the output station 0, and then the apparatusstops due to the operating arm 139 of switch 137 moving up and openingcontacts 137a and closing contacts 1370 of switch 137 when the lastplate P is pulled forward from input station I to exposure station E.With these contacts so set, on the last cycle of operation of timingmotor lCS, switch lCS-2 closes at 2% seconds energizing the upper coillLRU of latch relay lLR (in line 193) and the lower coil 3LRD of latchrelay 3LR (in line 191). Contacts lLRU-2 in circuit 213 open todeenergize the exposure lamp 209. Contacts lLRD-l (line 197) open todeenergize relay lTR placing its contacts back in starting position.Closure of contacts 3LRD-l (line 179) results in energization of theupper coil 4LRU of latch relay 4LR and attendant closure of contacts4LRU-l (line 175 and 4LRU-2 (line 177). On closure of contacts 4LRU-1 inline 175, lamp 0C is energized to indicate that the apparatus is offcycle." On closure of 4LRU-2 in line 177, the coil of timing relay 2TRis energized to start its timing interval (which may be 2 minutes, forexample). Contacts 2TR1 (line 201) remain closed to maintain the lowercoil 4LRD of latch relay 4LR energized and thus maintain contacts 4LRD-1open for this interval. Thus, even though switch lPB may be actuatedbefore the end of this interval, relay ILR will not be energized and,accordingly, exposure lamp 209 cannot be energized until after thisinterval. Also, on. energization of coil 3LRD, contacts 3LRU-2 (in line203) close to energize the coil of relay lCR. Contacts lCR-l (line 161),lCR-Z (line 205) and lCR-3 (line 207) open, thus preventing solenoidvalve V. and the motor for driving the vacuum pump 123 from beingenergized and also preventing stopping of timing motor lCS at 20seconds. The conveyor drive motor 45, in operation as a result of switchlCS-l having closed at 2 seconds, functions to pull the last plate P outof the exposure station E to the output station 0, and is deenergizedwhen the bar 53 pulling this plate actuates operating arm of switch 143.At 23 seconds, switch 1CS-9 (in line 181) closes, energizing the uppercoils ZLRU and 3LRU of latch relays ZLR and 3LR. Contacts 2L- RU-l (line181) and 2LRD-1 (line 167) open, thus deenergizing timing motor lCS.Contacts 3LRD-1, 3LRD-2, 3L- RU-l and liLRU-Z all return to theirstarting position. The coil of relay lCR is deenergized so that itscontacts return to starting position.

lnthe event only one plate is fed through the apparatus with switch 155set for automatic cycling (open), the plate goes through as abovedescribed and the apparatus stops in the same manner as above describedfor the last plate of a succession of plates fed through the apparatus.

For manual operation, e.g., for feeding only one plate through themachine, switch 155 (in line 157) is closed. This energizes the coil ofrelay 2CR. Contacts ZCR-S in circuit 213 close to energize the exposurelamp 209. A warmup period (e.g., 1 minute) should be allowed for thelamp 209 to warm up before starting to feed work through the apparatus.The contacts of the other relays will be as shown in FIG. 8, and lampsPO and R will be on to indicate that power is on and that the apparatusis ready.

A plate P with a film F thereon is placed on the table top plate 23 atstation I and attached to the bar 53 at station I. Then, push buttonswitch lPB is momentarily closed. This energizes the lower coil lLRD oflatch relay lLR, closing contacts lLRD-l and 1LRD-2 (line 197) toenergize lamp to indicate the operation is on, and to energize the lowercoil ZLRD of relay ZLR via lines 199 and 195 (contacts 2CR-2 and 1370being closed). Contacts ZLRD-l close to energize the timing motor 1138.Switch 1CS1 closes at 2 seconds to energize the motor 45 to drive theconveyor 1. with switch 143 closing to establish a holding circuit forthe motor when the bar 53 which was under arm 145 of switch 143 movesout from under the arm. Switch lCS-l opens at 5 seconds, but motor 45remains energized via said holding circuit until it is broken by theopening of switch 143 by the next bar 53 coming under the arm 143. Thisoccurs at about 7 seconds. At this point, the plate! with film F thereonis in the exposure station E At 8 seconds, switches lCS-3 (in line 161)and 1CS-{4 (in line 207) close, resulting (as before) in energizstion ofsolenoid valve V to lower the window assembly 59 and in energization ofmotor 125 to drive vacuum pump 123 to draw a vacuum for pressurizing ofthe plate and film.

I At 20 seconds, cam switch 1CS-5 (in line 205) is momentarily closed(as before) to effect energization of coil VTRC and motor VTRM ofvariable timing relay VTR, and deenergization of motor lCS. This effectsopening of the shutter of light source 7 (as before) to expose the plateP. When motor VTRM has timed out the exposure interval, contacts VTR-l(line 164) open as before to stop the motor and deenergize the coil VTRC of relay VTR, and to restart the timing motor lCS.

With motor lCS again in operation. at 2.2 seconds, switch 1CS-4 opens todeenergim the vacuum pump motor 125.

At 22% seconds, switch 1C8 opens for raising of window assembly 59 (asbefore)- Motor lCS continues to run through 0, and at 2 seconds switchlCS-l closes, starting motor 45 to resume operation of conveyor 1 (asbefore). This pulls the exposed plate P and the film F thereon out ofexposure station E to the output station D, motor 45 stopping when thebar 53 exiting from station E comes under arm 145 and actuates switch143.

At 2% seconds, switch lCS-Z closes, energizing the upper coil lLRU oflatch relay ILR (in line 193) and the lower coil 3LRD oflatch relay 3LR(in line 191). Contacts ILRD-1 (line 197) thereupon opento extinguishthe ()N" lamp 0. Also. contacts ;LBU-Q (line 203,) close to energizerelay ICR. with resulting opening of contacts lCll-l (line 161), lCR-Z(line 205) and 1CR3 (line 207) to prevent energizetion of solenoid valveV and motor 125 and also to prevent stopping of motor lCS (as before).

At 23 seconds, switch lCS-Q (in line 181) closes, to effect stopping ofmotor 168 and return of the contacts of latch relay SLR and the contactsof relay ICR to their starting position, as before.

It is possible to cfi'ect continued feeding of plates P to be exposedthrough the apparatus with switchin its manual setting (i.e., closed),by applying a plate P and film F to the conveyor] at input station Iduring each dwell of the conveyor (thus actuating switch 137), but, indistinction to automatic continued feeding as above described, when thelast plate P has been fed through the apparatus, the exposure lamp 209is not automatically deenergized.

From the above, it will appear that the apparatus is adaptedautomatically to handle plates P and films F through the expo sureprocedure, simply by applying a plate and a film to the conveyor 1(i.e., attaching the plate and film to a bar 53 via pins 55 or othersuitable means) during the dwell interval of the conveyor. The film maybe lifted away from the exposed plate at station 0, and the exposedplate fed forward away from station 0 to an automatic plate processor.The switch 137 functions to detect whether or not a plate has beenapplied to the conveyor 1 at the input station I, and stops theoperation of the apparatus if a plate has not been applied thereto aftercompleting the exposure of a plate at the exposure station E and theconveyance of the latter plate to the output station 0.

in view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As various changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

What is claimed is:

1. Apparatus for exposing photosensitized plates comprising an endlessconveyor having an upper reach movable in a predetermined path and alower return reach. means for intermittently driving the conveyorintermittently to convey a plate carried by said upper reach togetherwith a film on the upper face of said plate along said path from a firststation at which the plate and film may be applied to the conveyor to asecond station at which the plate is exposed to light through the filmand thence to a third station, means for pressing the plate and film atthe second station, said pressing means comprising means movableupwardly and downwardly above said upper reach adapted to be raised fromthe upper reach to permit the conveyor to move a plate with a filmthereon from the first to the second station and to move an exposedplate with a film thereon out of the second station to the thirdstation, and adapted to be lowered for pressing a plate and film at thesecond station for exposure of the plate while the conveyor is stopped,and a light source for exposing the plate at the second station to lightthrough the film while pressed by said pressing means.

2. Apparatus for exposing photosensitized plates comprising an endlessconveyor movable intennittently to convey a plate with a film thereonfrom a first station at which the plate and film may be applied to theconveyor to a second station at which the plate is exposed to lightthrough the film and thence to a third station, means for pressing theplate and film at the second station, said means being adapted to beopened to permit the conveyor to move a plate with a film thereon fromthe first to the second station and to move an exposed plate with a filmthereon out of the second station to the third station, and adapted tobe closed for pressing a plate and film. at the second station forexposure of the plate while the conveyor is stopped, and a lightsource-for exposing the plate at the second station to light through thefilm while pressed by said pressing means. and control means actingautomatically to close said. pressing means when the conveyor has moveda plate with a film thereon from the first to the second station andthenacting to operate said light source to expose the plate at the secondstation for an exposure interval.

3. Apparatus as set forth in claim 2 wherein the control means actsautomatically to open said pressing means on completion of exposure of aplate at the second station, and

then acts to operate the Conveyor for an interval to move the exposedplate with a film thereon out of the second station to the thirdstation.

4. Apparatus as set forth in claim 3 wherein said control means includesmeans for varying the length of the exposure interval.

5. Apparatus as set forth in claim 3 wherein the conveyor is adapted tobring another plate with a film thereon from the first to second stationwhen it is operated for its said interval, and wherein said controlmeans acts automatically to close said pressing means when the conveyorstops at the end of its said interval and then acts to operate saidlight source to expose the plate at the second station for an exposureinterval.

6. Apparatus as set forth in claim 5 wherein said control means includesmeans for detecting whether or not a plate has been applied to theconveyor at the first station and stopping operation of the apparatus ifa plate has not been applied.

7. Apparatus as set forth in claim 6 wherein said plate-detecting meansacts to stop the apparatus after completion of exposure of the plate atthe second station and conveyance of the latter plate to the thirdstation.

8. Apparatus as set forth in claim 1 wherein said pressing means whenclosed forms a vacuum chamber and wherein means is provided forevacuating said chamber.

9. Apparatus for exposing photosensitized plates comprising an endlessconveyor movable intermittently to convey a plate with a film thereonfrom a first station at which the plate and film may be applied to theconveyor to a second station at which the plate is exposed to lightthrough the film and thence to a third station, means for pressing theplate and film at the second station, said means being adapted to beopened to permit the conveyor to move a plate with a film thereon fromthe first to the second station and to move an exposed plate with a filmthereon out of the second station to the third station, and adapted tobe closed for pressing a plate and film at the second station forexposure of the plate while the conveyor is stopped, and a light sourcefor exposing the plate at the second station to light through the filmwhile pressed by said pressing means, said pressing means comprising alight-transmitting panel movable between an open retracted position anda closed position engaging the film on the plate at the second station.

10. Apparatus as set forth in claim 9 wherein said panel when closedforms a vacuum chamber and wherein means is provided for evacuating saidchamber.

11. Apparatus for exposing photosensitized plates comprising an endlessconveyor movable intermittently to convey a plate with a film thereonfrom a first station at which the plate and film may be applied to theconveyor to a second station at which the plate is exposed to lightthrough the film and thence to a third station, a flexible presser padat the second station, the plate with the film thereon being conveyedfrom the first station onto said pad, a light-transmitting panel abovethe pad, means mounting said panel for movement between a raisedretracted position spaced from the pad and a lowered closed position inperipheral sealing engagement with the pad forming a vacuum chamber,means for evacuating said chamber for pressing of the plate and film insaid chamber by the pad against the panel for exposure of the plate,said panel when in retracted position permitting the conveyor to move aplate with a film thereon from the first station onto the pad at thesecond station and to move an exposed plate and the film thereon off thepad and out of the second station to the third station, and a lightsource for exposing the plate at the second station to light through thefilm thereon via said panel while pressed against said panel.

12. Apparatus as set forth in claim 11 having control means forautomatically raising said panel on completion of exposure of a plate atthe second station and then operating the conveyor for an interval tomove an exposed plate with a film thereon off the pad and out of thesecond station to the third station.

13. Apparatus as set forth in claim 12 wherein the control means actsautomatically to lower said panel when the conveyor has moved a platewith a film thereon onto the pad at the second station, then acts tooperate said evacuating means, and then acts to operate said lightsource to expose the plate at the second station for an exposureinterval.

14. Apparatus as set forth in claim 13 wherein the control means actsautomatically to stop the operation of said evacuating means and toraise said panel on completion of exposure of a plate at the secondstation, and then acts to operate the conveyor for an interval to movethe exposed plate with a film thereon off the pad and out of the secondstation to the third station.

15. Apparatus as set forth in claim 14 wherein the conveyor is adaptedto bring another plate with a film thereon from the first station ontothe pad at the second station when it is operated for its said interval,and wherein said control means acts automatically to lower said panelwhen the conveyor stops at the end of its said interval, then acts tooperate said evacuating means, and then acts to operate said lightsource to expose the plate at the second station for an exposureinterval.

16. Apparatus as set forth in claim 15 having means for detectingwhether or not a plate has been applied to the conveyor at the firststation and stopping operation of the apparatus if a plate has not beenapplied.

17. Apparatus as set forth in claim 16 wherein said plate-detectingmeans acts to stop the apparatus after completion of exposure of theplate at the second station and conveyance of the latter plate to thethird station.

18. Apparatus as set forth in claim 11 wherein said conveyor comprises apair of endless chains having upper reaches extending along oppositesides of said pad, and bars extending transversely between said chainsspaced at intervals along their length, each of said bars having meansthereon for attachment of a plate and film thereto.

19. Apparatus as set forth in claim 18 having a tabletop member at thefirst station and a tabletop member at the third station, the pad beingbetween said tabletop members and generally flush with the top surfacesthereof, the bars passing over said tabletop members and said pad.

20. Apparatus as set forth in claim 19 wherein said lighttransmittingpanel is mounted for up and down movement in a frame spanning theapparatus above the pad at the second statron.

21. Apparatus as set forth in claim 20 wherein the light source iscarried by means extending up from said frame.

22. Apparatus as set forth in claim 20 having cam means actuated by anair cylinder on said frame for moving said panel up and down.

23. Apparatus as set forth in claim 22 having an electric motor fordriving said conveyor, a solenoid valve controlling said air cylinderand control means for actuating said valve to cause said cylinder toraise said panel on completion of exposure of a plate at the secondstation and then energizing said motor to operate the conveyor for aninterval to move an exposed plate out of the second station to the thirdstation and to bring another plate with a film thereon from the first tothe second station, and including a switch operable by a bar of saidconveyor as it brings a plate to the third station for deenergizing saidmotor to stop the conveyor, and means for actuating said valve to causesaid cylinder to close said panel when the conveyor stops and thenoperating said light source to expose the plate at the second stationfor an exposure interval.

24. Apparatus as set forth in claim 23 having a switch with an operatingarm projecting up through an opening in the table top member at thefirst station for detecting whether or not a plate has been applied tothe table top member at the first station and stopping operation of theapparatus if a plate has not been applied.

25. Apparatus as set forth in claim 24 wherein said plate-detectingswitch acts to stop the operation of the apparatus after completion ofexposure of the plate at the second station and conveyance of this plateby the conveyor to the third station.

26. Apparatus for exposing photosensitized plates comprising conveyormeans movable intermittently to convey a plate from a first station atwhich the plate may be applied to the conveyor means to a second stationat which the plate is exposed to light through a film and thence out ofthe second station, means for pressing the plate and film atthe secondstation, said pressing means being adapted to be opened to permit theconveyor means to move a plate from the first to the second station andto move an exposed plate out of the second station, and adapted to beclosed for pressing a plate and film at the second station for exposureof the plate while the conveyor means is stopped, a light source forexposing the plate at the second station to light through the film whilepressed by said pressing means, and control means acting automaticallyto close said pressing means when the conveyor means has moved a platefrom the first station to the second station, and then acting to operatesaid light source to expose the plate through the film at said secondstation for an exposure interval.

27. Apparatus for exposing photosensitized plates comprising an endlessconveyor movable intermittently to convey a plate from a first stationat which the-plate may be applied to the conveyor to a second station atwhich the plate is exposed to light through a film and thence out of thesecond station, a flexible presser pad at the second station, the platebeing conveyed from the first station onto said pad, alight-transmitting panel above the pad, means mounting said panel formovement between a raised retracted position spaced from the pad andlowered closed position in peripheral sealing engagement with the padforming a vacuum chamber, means for evacuating said chamber for pressingof the plate and film in said chamber by the pad against the panel forexposure of the plate, said panel when in retracted position permittingthe conveyor to move a plate from the first station onto the pad at thesecond station and to move an exposed plate off the pad and out of thesecond station, and a light source for exposing the plate at the secondstation to light through the film thereon via said panel while pressedagainst said panel.

* i i t

1. Apparatus for exposing photosensitized plates comprising an endlessconveyor having an upper reach movable in a predetermined path and alower return reach, means for intermittently driving the conveyorintermittently to convey a plate carried by said upper reach togetherwith a film on the upper face of said plate along said path from a firststation at which the plate and film may be applied to the conveyor to asecond station at which the plate is exposed to light through the filmand thence to a third station, means for pressing the plate and film atthe second station, said pressing means comprising means movableupwardly and downwardly above said upper reach adapted to be raised fromthe upper reach to permit the conveyor to move a plate with a filmthereon from the first to the second station and to move an exposedplate with a film thereon out of the second station to the thirdstation, and adapted to be lowered for pressing a plate and film at thesecond station for exposure of the plate while the conveyor is stopped,and a light source for exposing the plate at the second station to lightthrough the film while pressed by said pressing means.
 2. Apparatus forexposing photosensitized plates comprising an endless conveyor movableintermittently to convey a plate with a film thereon from a firststation at which the plate and film may be applied to the conveyor to asecond station at which the plate is exposed to light through the filmand thence to a third station, means for pressing the plate and film atthe second station, said means being adapted to be opened to permit theconveyor to move a plate with a film thereon from the first to thesecond station and to move an exposed plate with a film thereon out ofthe second station to the third station, and adapted to be closed forpressing a plate and film at the second station for expOsure of theplate while the conveyor is stopped, and a light source for exposing theplate at the second station to light through the film while pressed bysaid pressing means, and control means acting automatically to closesaid pressing means when the conveyor has moved a plate with a filmthereon from the first to the second station and then acting to operatesaid light source to expose the plate at the second station for anexposure interval.
 3. Apparatus as set forth in claim 2 wherein thecontrol means acts automatically to open said pressing means oncompletion of exposure of a plate at the second station, and then actsto operate the conveyor for an interval to move the exposed plate with afilm thereon out of the second station to the third station. 4.Apparatus as set forth in claim 3 wherein said control means includesmeans for varying the length of the exposure interval.
 5. Apparatus asset forth in claim 3 wherein the conveyor is adapted to bring anotherplate with a film thereon from the first to second station when it isoperated for its said interval, and wherein said control means actsautomatically to close said pressing means when the conveyor stops atthe end of its said interval and then acts to operate said light sourceto expose the plate at the second station for an exposure interval. 6.Apparatus as set forth in claim 5 wherein said control means includesmeans for detecting whether or not a plate has been applied to theconveyor at the first station and stopping operation of the apparatus ifa plate has not been applied.
 7. Apparatus as set forth in claim 6wherein said plate-detecting means acts to stop the apparatus aftercompletion of exposure of the plate at the second station and conveyanceof the latter plate to the third station.
 8. Apparatus as set forth inclaim 1 wherein said pressing means when closed forms a vacuum chamberand wherein means is provided for evacuating said chamber.
 9. Apparatusfor exposing photosensitized plates comprising an endless conveyormovable intermittently to convey a plate with a film thereon from afirst station at which the plate and film may be applied to the conveyorto a second station at which the plate is exposed to light through thefilm and thence to a third station, means for pressing the plate andfilm at the second station, said means being adapted to be opened topermit the conveyor to move a plate with a film thereon from the firstto the second station and to move an exposed plate with a film thereonout of the second station to the third station, and adapted to be closedfor pressing a plate and film at the second station for exposure of theplate while the conveyor is stopped, and a light source for exposing theplate at the second station to light through the film while pressed bysaid pressing means, said pressing means comprising a light-transmittingpanel movable between an open retracted position and a closed positionengaging the film on the plate at the second station.
 10. Apparatus asset forth in claim 9 wherein said panel when closed forms a vacuumchamber and wherein means is provided for evacuating said chamber. 11.Apparatus for exposing photosensitized plates comprising an endlessconveyor movable intermittently to convey a plate with a film thereonfrom a first station at which the plate and film may be applied to theconveyor to a second station at which the plate is exposed to lightthrough the film and thence to a third station, a flexible presser padat the second station, the plate with the film thereon being conveyedfrom the first station onto said pad, a light-transmitting panel abovethe pad, means mounting said panel for movement between a raisedretracted position spaced from the pad and a lowered closed position inperipheral sealing engagement with the pad forming a vacuum chamber,means for evacuating said chamber for pressing of the plate and film insaid chamber by the pad against the panel for exposure of the plate,said panel when in retracted position permitting the conveyor to move aplate with a film thereon from the first station onto the pad at thesecond station and to move an exposed plate and the film thereon off thepad and out of the second station to the third station, and a lightsource for exposing the plate at the second station to light through thefilm thereon via said panel while pressed against said panel. 12.Apparatus as set forth in claim 11 having control means forautomatically raising said panel on completion of exposure of a plate atthe second station and then operating the conveyor for an interval tomove an exposed plate with a film thereon off the pad and out of thesecond station to the third station.
 13. Apparatus as set forth in claim12 wherein the control means acts automatically to lower said panel whenthe conveyor has moved a plate with a film thereon onto the pad at thesecond station, then acts to operate said evacuating means, and thenacts to operate said light source to expose the plate at the secondstation for an exposure interval.
 14. Apparatus as set forth in claim 13wherein the control means acts automatically to stop the operation ofsaid evacuating means and to raise said panel on completion of exposureof a plate at the second station, and then acts to operate the conveyorfor an interval to move the exposed plate with a film thereon off thepad and out of the second station to the third station.
 15. Apparatus asset forth in claim 14 wherein the conveyor is adapted to bring anotherplate with a film thereon from the first station onto the pad at thesecond station when it is operated for its said interval, and whereinsaid control means acts automatically to lower said panel when theconveyor stops at the end of its said interval, then acts to operatesaid evacuating means, and then acts to operate said light source toexpose the plate at the second station for an exposure interval. 16.Apparatus as set forth in claim 15 having means for detecting whether ornot a plate has been applied to the conveyor at the first station andstopping operation of the apparatus if a plate has not been applied. 17.Apparatus as set forth in claim 16 wherein said plate-detecting meansacts to stop the apparatus after completion of exposure of the plate atthe second station and conveyance of the latter plate to the thirdstation.
 18. Apparatus as set forth in claim 11 wherein said conveyorcomprises a pair of endless chains having upper reaches extending alongopposite sides of said pad, and bars extending transversely between saidchains spaced at intervals along their length, each of said bars havingmeans thereon for attachment of a plate and film thereto.
 19. Apparatusas set forth in claim 18 having a tabletop member at the first stationand a tabletop member at the third station, the pad being between saidtabletop members and generally flush with the top surfaces thereof, thebars passing over said tabletop members and said pad.
 20. Apparatus asset forth in claim 19 wherein said light-transmitting panel is mountedfor up and down movement in a frame spanning the apparatus above the padat the second station.
 21. Apparatus as set forth in claim 20 whereinthe light source is carried by means extending up from said frame. 22.Apparatus as set forth in claim 20 having cam means actuated by an aircylinder on said frame for moving said panel up and down.
 23. Apparatusas set forth in claim 22 having an electric motor for driving saidconveyor, a solenoid valve controlling said air cylinder and controlmeans for actuating said valve to cause said cylinder to raise saidpanel on completion of exposure of a plate at the second station andthen energizing said motor to operate the conveyor for an interval tomove an exposed plate out of the second station to the third station andto bring another plate with a film thereon from the first to the secondstation, and including a switch operable by a bar of said conveyor as Itbrings a plate to the third station for deenergizing said motor to stopthe conveyor, and means for actuating said valve to cause said cylinderto close said panel when the conveyor stops and then operating saidlight source to expose the plate at the second station for an exposureinterval.
 24. Apparatus as set forth in claim 23 having a switch with anoperating arm projecting up through an opening in the table top memberat the first station for detecting whether or not a plate has beenapplied to the table top member at the first station and stoppingoperation of the apparatus if a plate has not been applied. 25.Apparatus as set forth in claim 24 wherein said plate-detecting switchacts to stop the operation of the apparatus after completion of exposureof the plate at the second station and conveyance of this plate by theconveyor to the third station.
 26. Apparatus for exposingphotosensitized plates comprising conveyor means movable intermittentlyto convey a plate from a first station at which the plate may be appliedto the conveyor means to a second station at which the plate is exposedto light through a film and thence out of the second station, means forpressing the plate and film at the second station, said pressing meansbeing adapted to be opened to permit the conveyor means to move a platefrom the first to the second station and to move an exposed plate out ofthe second station, and adapted to be closed for pressing a plate andfilm at the second station for exposure of the plate while the conveyormeans is stopped, a light source for exposing the plate at the secondstation to light through the film while pressed by said pressing means,and control means acting automatically to close said pressing means whenthe conveyor means has moved a plate from the first station to thesecond station, and then acting to operate said light source to exposethe plate through the film at said second station for an exposureinterval.
 27. Apparatus for exposing photosensitized plates comprisingan endless conveyor movable intermittently to convey a plate from afirst station at which the plate may be applied to the conveyor to asecond station at which the plate is exposed to light through a film andthence out of the second station, a flexible presser pad at the secondstation, the plate being conveyed from the first station onto said pad,a light-transmitting panel above the pad, means mounting said panel formovement between a raised retracted position spaced from the pad andlowered closed position in peripheral sealing engagement with the padforming a vacuum chamber, means for evacuating said chamber for pressingof the plate and film in said chamber by the pad against the panel forexposure of the plate, said panel when in retracted position permittingthe conveyor to move a plate from the first station onto the pad at thesecond station and to move an exposed plate off the pad and out of thesecond station, and a light source for exposing the plate at the secondstation to light through the film thereon via said panel while pressedagainst said panel.